History

The clinical spectrum of yellow fever (YF) ranges from a minimally symptomatic flulike illness to a catastrophic illness complicated by hemorrhage and organ failure (primarily the liver and kidney). It develops in a number of distinct phases (not all of which invariably occur).

The abortive phase may extend over 1 day or longer. Recovery occurs without further symptoms.

The period of intoxication may last 3-5 days. Liver failure, hemorrhagic diathesis, and kidney failure occur. This period develops in approximately 15% of all cases. This stage is fatal in 1-50% of cases that develop toxicity. Previous symptoms and new symptoms include fever with high temperatures, chills, anxiety, confusion, lethargy, prostration, jaundice, epistaxis, anorexia, epigastric pain, nausea, vomiting, hematemesis, melena, lumbosacral pain, and decreased urine output. Complications include bacterial pneumonia and sepsis.

The period of convalescence may last days to weeks. The patient recovers completely, without sequelae. Complications may include protracted weakness and fatigability.

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Physical Examination

The Pan American Health Organization has published a case definition for YF to aid in surveillance. By this definition, YF is an illness characterized by acute onset of fever followed by jaundice within 2 weeks of the onset of first symptoms plus 1 of the following:

Bleeding from the nose, gums, gastrointestinal (GI) tract, or skin

Death within 3 weeks of illness onset

A case of YF is classified as suspected if it meets the clinical definition or if other causes of fever or jaundice are excluded. A suspected YF case can be confirmed by laboratory testing or by being epidemiologically linked to a laboratory-confirmed case or outbreak.

Data to be reported to public health authorities include patient-specific identifier, age or date of birth, location, laboratory results, vaccination history, outcome of infection (alive, dead, unknown), case classification, and date of death (if dead).

Physical examination findings are nonspecific and may include the following:

Hemorrhagic diathesis - YF virus directly injures the liver, kidney, and heart; a hemorrhagic diathesis progressing to disseminated intravascular coagulation (DIC) is not uncommon in the toxic form of the disease, because of hepatic damage, thrombocytopenia, and perhaps other factors

This female Aedes aegypti mosquito is shown here after landing on a human host. The A aegypti mosquito is a known transmitter of both dengue fever and yellow fever. A aegypti is sometimes referred to as the yellow fever mosquito. The viruses are transferred to the host when bitten by a female mosquito. Image courtesy of the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO).

William H Shoff, MD, DTM&H Former Director, PENN Travel Medicine; Former Associate Professor, Department of Emergency Medicine, Hospital of the University of Pennsylvania, University of Pennsylvania School of Medicine

Robert W Tolan Jr, MD Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine